The present invention relates to a work roll for a metal rolling mill and a manufacturing method therefor, and, more particularly, to a work roll for a shift type 6-high rolling mill having great shaft strength and which can thereby be suitably used for cold metal rolling and a manufacturing method therefor.
In a roll for a metal rolling mill, the roll surface is subjected to a thermal shock due to a slip taking place between the roll and a material to be rolled during the rolling operation or due to an accident in which the material to be rolled is wound to the roll. If the thermal shock is too large, cracks are generated on the surface of the roll.
The resistance of the roll to the thermal shock can be effectively improved by conducting tempering at a high temperature in the heat treatment to be applied to the roll surface, that is, in the quench-and-temper process.
A conventional work roll is disclosed in, for example, Japanese Patent Unexamined Publication No. 63-60258, wherein the work roll has a composition consisting of 1.2 to 2.5% of carbon, 0.8 to 3.0% of silicon, 1% or less of manganese, 3.0 to 6.0% of chromium and 0.2% or less of molybdenum is subjected to the quench-and-temper process. In the above-described process, in order to obtain Shore hardness (Hs) 93 or more, the tempering temperature has been arranged to be 160.degree. or lower. In this case, if the tempering temperature is higher than 160.degree. C. for the purpose of improving the heat resistance and thermal shock resistance, the hardness exceeding Hs 93 cannot be obtained and the wear resistance deteriorates. As a result, the rolling becomes unsatisfactory.